Author

Date of Graduation

Document Type

Degree Name

Degree Level

Graduate

Department

Food Science

Advisor

Ya-Jane Wang

Committee Member

Terry Siebenmorgen

Second Committee Member

Andronikos Mauromoustako

Keywords

Parboiling, Rice, Biological sciences

Abstract

It is estimated that over 20% of world rice production is parboiled, and parboiled rice properties are affected by parboiling conditions as well as by feedstock properties. The objective of this study was to investigate the impacts of crop year and ageing on parboiled rice properties under different parboiling conditions. Freshly harvested and aged RoyJ, a pureline, and CL XL745, a hybrid, from 2014 and 2015 crop years were soaked at 8C, 4C below onset gelatinization temperature (GT), at onset GT, or 4C above GT for 3 h, and steamed at 100C, 110C, or 120C for 10, 15, or 20 min prior to gentle drying and then characterization. RoyJ had a greater amylose content and a lower protein content than CL XL745 for both crop years. Regardless of parboiling conditions, CL XL745 had lower percentages of deformed kernels, greater head rice yields, lower water absorption, and greater cooked rice hardness than RoyJ, which was attributed to its greater protein content. After parboiling, both cultivars displayed increased head rice yield, breaking force, water absorption, and cooked rice hardness, and reduced deformed kernels and soluble solids in 2014 than in 2015. Aged rice had increased cooked rice hardness, and decreased deformed kernels, whiteness, pasting viscosities, and soluble solids compared with freshly harvested rice when subjected to the same parboiling conditions. Similar properties could not be obtained from fresh and aged rice even at different parboiling conditions. The present study demonstrates that parboiled rice properties are significantly influenced by ageing and crop year, and suggests that protein may have a greater influence than amylose on parboiled rice properties.